Chapter 22 MACHINING OPERATIONS AND MACHINE TOOLS

1. Chapter 22MACHINING OPERATIONS AND MACHINE TOOLS • Turning and Related Operations • Drilling and Related Operations • Milling • Machining Centers and Turning Centers • Other Machining Operations • High Speed Machining ISE 316 - Manufacturing Processes Engineering

2. Machining A material removal process in which a sharp cutting tool is used to mechanically cut away material so that the desired part geometry remains • Most common application: to shape metal parts • Machining is the most versatile and accurate of all manufacturing processes in its capability to produce a diversity of part geometries and geometric features • Casting can also produce a variety of shapes, but it lacks the precision and accuracy of machining ISE 316 - Manufacturing Processes Engineering

3. Classification of Machined Parts • Rotational - cylindrical or disk‑like shape • Nonrotational (also called prismatic) - block‑like or plate‑like Figure 22.1 ‑ Machined parts are classified as: (a) rotational, or (b) nonrotational, shown here by block and flat parts ISE 316 - Manufacturing Processes Engineering

4. Machining Operations and Part Geometry Each machining operation produces a characteristic part geometry due to two factors: • Relative motions between the tool and the workpart • Generating – part geometry is determined by the feed trajectory of the cutting tool • Shape of the cutting tool • Forming – part geometry is created by the shape of the cutting tool ISE 316 - Manufacturing Processes Engineering

5. Figure 22.2 ‑ Generating shape: (a) straight turning, (b) taper turning, (c) contour turning, (d) plain milling, (e) profile milling ISE 316 - Manufacturing Processes Engineering

6. Figure 22.3 ‑ Forming to create shape: (a) form turning, (b) drilling, and (c) broaching ISE 316 - Manufacturing Processes Engineering

7. Figure 22.4 ‑ Combination of forming and generating to create shape: (a) thread cutting on a lathe, and (b) slot milling (old:Fig.25.41) ISE 316 - Manufacturing Processes Engineering

8. Turning A single point cutting tool removes material from a rotating workpiece to generate a cylindrical shape • Performed on a machine tool called a lathe • Variations of turning that are performed on a lathe: • Facing • Contour turning • Chamfering • Cutoff • Threading ISE 316 - Manufacturing Processes Engineering

9. Figure 22.5 ‑ Turning operation ISE 316 - Manufacturing Processes Engineering

10. Facing Tool is fed radially inward Figure 22.6 (a) facing ISE 316 - Manufacturing Processes Engineering

11. Contour Turning Instead of feeding the tool parallel to the axis of rotation, tool follows a contour that is other than straight, thus creating a contoured form Figure 22.6 (c) contour turning ISE 316 - Manufacturing Processes Engineering

12. Chamfering Cutting edge cuts an angle on the corner of the cylinder, forming a "chamfer" Figure 22.6 (e) chamfering ISE 316 - Manufacturing Processes Engineering

13. Cutoff Tool is fed radially into rotating work at some location to cut off end of part Figure 22.6 (f) cutoff ISE 316 - Manufacturing Processes Engineering

14. Threading Pointed form tool is fed linearly across surface of rotating workpart parallel to axis of rotation at a large feed rate, thus creating threads Figure 22.6 (g) threading ISE 316 - Manufacturing Processes Engineering

15. Figure 22.7 Diagram of an engine lathe, showing its principal components ISE 316 - Manufacturing Processes Engineering

16. Methods of Holding the Work in a Lathe • Holding the work between centers • Chuck • Collet • Face plate ISE 316 - Manufacturing Processes Engineering

17. Holding the Work Between Centers Figure 22.8 (a) mounting the work between centers using a "dog” ISE 316 - Manufacturing Processes Engineering

18. Chuck Figure 22.8 (b) three‑jaw chuck ISE 316 - Manufacturing Processes Engineering

19. Collet Figure 22.8 (c) collet ISE 316 - Manufacturing Processes Engineering

20. Face Plate Figure 22.8 (d) face plate for non‑cylindrical workparts ISE 316 - Manufacturing Processes Engineering

21. Turret Lathe Tailstock replaced by “turret” that holds up to six tools • Tools rapidly brought into action by indexing the turret • Tool post replaced by four‑sided turret to index four tools • Applications: high production work that requires a sequence of cuts on the part ISE 316 - Manufacturing Processes Engineering

22. Chucking Machine • Uses chuck in its spindle to hold workpart • Parts cannot be mounted between centers • Cutting tool actions controlled automatically • Operator’s job: to load and unload parts • Applications: short, light‑weight parts ISE 316 - Manufacturing Processes Engineering

23. Bar Machine • Similar to chucking machine except collet replaces chuck, permitting long bar stock to be fed through headstock • At the end of the machining cycle, a cutoff operation separates the new part • Highly automated (the term automatic bar machine is often used) • Applications: high production of rotational parts ISE 316 - Manufacturing Processes Engineering

24. Automatic Screw Machine • Same as automatic bar machine but smaller • Applications: high production of screws and similar small hardware items; hence, its name ISE 316 - Manufacturing Processes Engineering

25. Multiple Spindle Bar Machines • More than one spindle, so multiple parts machined simultaneously by multiple tools • Example: six spindle automatic bar machine works on six parts at a time • After each machining cycle, spindles (including collets and workbars) are indexed (rotated) to next position ISE 316 - Manufacturing Processes Engineering

26. NEW NCs or CNCs • high speed spindle (> 40,000 rpm) • high feed rate drive ( > 600 ipm) • high precision ( < 0.0001" accuracy)

27. Figure 22.9 ‑ (a) Part produced on a six‑spindle automatic bar machine; and (b) sequence of operations to produce the part: (1) feed stock to stop, (2) turn main diameter, (3) form second diameter and spotface, (4) drill, (5) chamfer, and (6) cutoff ISE 316 - Manufacturing Processes Engineering

28. Boring • Difference between boring and turning: • Boring is performed on the inside diameter of an existing hole • Turning is performed on the outside diameter of an existing cylinder • In effect, boring is an internal turning operation • Boring machines • Horizontal or vertical - refers to the orientation of the axis of rotation of machine spindle ISE 316 - Manufacturing Processes Engineering

29. Figure 22.12 ‑ A vertical boring mill –for large, heavy workparts ISE 316 - Manufacturing Processes Engineering

30. Drilling • Creates a round hole in a workpart • Contrasts with boring which can only enlarge an existing hole • Cutting tool called a drill or drill bit • Customarily performed on a drill press Figure 21.3 (b) drilling ISE 316 - Manufacturing Processes Engineering

31. Through Holes vs. Blind Holes Through‑holes - drill exits the opposite side of work Blind‑holes – drill does not exit work on opposite side Figure 22.13 ‑ Two hole types: (a) through‑hole, and (b) blind hole ISE 316 - Manufacturing Processes Engineering

32. Reaming Used to slightly enlarge a hole, provide better tolerance on diameter, and improve surface finish • Figure 22.14 ‑ • Machining operations related to drilling: • Reaming ISE 316 - Manufacturing Processes Engineering

33. Tapping Used to provide internal screw threads on an existing hole Tool called a tap Figure 22.14 (b) tapping ISE 316 - Manufacturing Processes Engineering

34. Counterboring Provides a stepped hole, in which a larger diameter follows a smaller diameter partially into the hole Figure 22.14 (c) counterboring ISE 316 - Manufacturing Processes Engineering

35. Upright Drill Stands on the floor Bench Drill Similar but smaller and mounted on a table or bench Figure 22.15 ‑ Upright drill press ISE 316 - Manufacturing Processes Engineering

36. Radial Drill Large drill press designed for large parts Figure 22.16 ‑ Radial drill press (Willis Machinery and Tools) ISE 316 - Manufacturing Processes Engineering

37. Work Holding for Drill Presses • Workpart can be clamped in a vise, fixture, or jig • Vise - general purpose workholder with two jaws • Fixture - workholding device that is usually custom‑designed for the particular workpart • Drill jig – similar to fixture but also provides a means of guiding the tool during drilling ISE 316 - Manufacturing Processes Engineering

38. Milling Machining operation in which work is fed past a rotating tool with multiple cutting edges • Axis of tool rotation is perpendicular to feed direction • Creates a planar surface; other geometries possible either by cutter path or shape • Other factors and terms: • Milling is an interrupted cutting operation • Cutting tool called a milling cutter, cutting edges called "teeth" • Machine tool called a milling machine ISE 316 - Manufacturing Processes Engineering

39. Figure 21.3 ‑ Two forms of milling: • peripheral milling, and (b) face milling ISE 316 - Manufacturing Processes Engineering

40. Peripheral Milling vs. Face Milling • Peripheral milling • Cutter axis is parallel to surface being machined • Cutting edges on outside periphery of cutter • Face milling • Cutter axis is perpendicular to surface being milled • Cutting edges on both the end and outside periphery of the cutter ISE 316 - Manufacturing Processes Engineering

41. Slab Milling The basic form of peripheral milling in which the cutter width extends beyond the workpiece on both sides • Figure 22.18 • slab milling ISE 316 - Manufacturing Processes Engineering

42. Slotting • Width of cutter is less than workpiece width, creating a slot in the work Figure 22.18 (b) Slotting ISE 316 - Manufacturing Processes Engineering

43. Conventional Face Milling Cutter overhangs work on both sides Figure 22.20 (a) conventional face milling ISE 316 - Manufacturing Processes Engineering

44. End Milling Cutter diameter is less than work width, so a slot is cut into part Figure 22.20 ‑ (c) end milling ISE 316 - Manufacturing Processes Engineering

45. Profile Milling Form of end milling in which the outside periphery of a flat part is cut Figure 22.20 (d) profile milling ISE 316 - Manufacturing Processes Engineering

46. Pocket Milling Another form of end milling used to mill shallow pockets into flat parts Figure 22.20 (e) pocket milling ISE 316 - Manufacturing Processes Engineering

47. Surface Contouring Ball‑nose cutter is fed back and forth across the work along a curvilinear path at close intervals to create a three dimensional surface form Figure 22.20 (f) surface contouring ISE 316 - Manufacturing Processes Engineering

48. Figure 22.23 (a) horizontal knee-and-column milling machine ISE 316 - Manufacturing Processes Engineering

49. Figure 22.23 (b) vertical knee‑and‑column milling machine ISE 316 - Manufacturing Processes Engineering

50. Machining Centers Highly automated machine tool capable of performing multiple machining operations under CNC control in one setup with minimal human attention • Typical operations are milling and drilling • Three, four, or five axes • Other features: • Automatic tool‑changing • Pallet shuttles • Automatic workpart positioning ISE 316 - Manufacturing Processes Engineering